Fair Value Level 3 Valuation Inputs (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2013		Dec. 31, 2012
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	$ 648	[1]	$ 218	[1]
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for sale, at lower of cost or fair value	802		208
Trading securities	2,685		2,286
Available-for-sale securities	18,979		25,034
Mortgage loans held for investment, at fair value	393,817		466,594
Assets, Fair Value Disclosure	417,607		495,561
Fannie Mae [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(684)		(793)
Fannie Mae [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	223,365		232,170
Long-term debt	(962)		(1,056)
Consolidated Trusts [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	13,877		10,800
Long-term debt	(14,414)		(11,647)
Consolidated Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	170,452		234,424
Long-term debt	(13,082)		(16,171)
Recurring Fair Value Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	2,685		2,286
Available-for-sale securities	18,979		25,034
Derivatives	(26)		14
Long-term debt	(889)		(1,528)
Assets, Fair Value Disclosure	24,392		30,129
Recurring Fair Value Measurements [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			71	[2]
Recurring Fair Value Measurements [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	1,411		1,319
Available-for-sale securities	6,965		7,447
Recurring Fair Value Measurements [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	595		675
Available-for-sale securities	5,799		7,837
Recurring Fair Value Measurements [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	110		117
Available-for-sale securities	2,958		3,147
Recurring Fair Value Measurements [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	520		104
Available-for-sale securities	3,239		6,564
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	465		544
Available-for-sale securities	2,549		3,333
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	7.40%	[3]	10.90%	[3]
Prepayment Speed (%)	0.80%	[3]	0.30%	[3]
Severity (%)	67.30%	[3]	80.00%	[3]
Spreads (bps)	3.75%	[3]	4.27%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	11.10%	[3]	23.00%	[3]
Prepayment Speed (%)	4.50%	[3]	7.90%	[3]
Severity (%)	90.50%	[3]	80.00%	[3]
Spreads (bps)	5.55%	[3]	6.57%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	8.70%	[3]	16.00%	[3]
Prepayment Speed (%)	2.50%	[3]	2.60%	[3]
Severity (%)	77.90%	[3]	80.00%	[3]
Spreads (bps)	4.07%	[3]	4.885%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	0.00%	[3]
Severity (%)	10.20%	[3]	65.00%	[3]
Spreads (bps)	1.75%	[3]	3.25%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	16.10%	[3]	27.40%	[3]
Prepayment Speed (%)	18.70%	[3]	14.40%	[3]
Severity (%)	99.20%	[3]	80.00%	[3]
Spreads (bps)	5.30%	[3]	6.60%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	8.20%	[3]	15.40%	[3]
Prepayment Speed (%)	4.80%	[3]	3.00%	[3]
Severity (%)	80.60%	[3]	77.80%	[3]
Spreads (bps)	4.296%	[3]	4.937%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	405		534
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	3.00%	[3]	1.00%	[3]
Severity (%)	65.00%	[3]	65.00%	[3]
Spreads (bps)	3.50%	[3]	4.50%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.00%	[3]	5.00%	[3]
Prepayment Speed (%)	13.80%	[3]	14.10%	[3]
Severity (%)	85.00%	[3]	85.00%	[3]
Spreads (bps)	6.79%	[3]	7.29%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	4.70%	[3]	4.70%	[3]
Prepayment Speed (%)	3.70%	[3]	3.60%	[3]
Severity (%)	83.70%	[3]	83.80%	[3]
Spreads (bps)	4.817%	[3]	5.858%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	145
Available-for-sale securities	1,886		2,285
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	10.80%	[3]
Prepayment Speed (%)	8.40%	[3]
Severity (%)	70.30%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	10.80%	[3]
Prepayment Speed (%)	8.40%	[3]
Severity (%)	70.30%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	10.80%	[3]
Prepayment Speed (%)	8.40%	[3]
Severity (%)	70.30%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	0.10%	[3]	0.20%	[3]
Severity (%)	0.10%	[3]	50.00%	[3]
Spreads (bps)	2.75%	[3]	3.00%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	14.20%	[3]	17.70%	[3]
Prepayment Speed (%)	31.70%	[3]	41.30%	[3]
Severity (%)	92.30%	[3]	70.00%	[3]
Spreads (bps)	5.55%	[3]	6.34%	[3]
Recurring Fair Value Measurements [Member] | Consensus with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	4.20%	[3]	3.60%	[3]
Prepayment Speed (%)	13.50%	[3]	10.00%	[3]
Severity (%)	61.50%	[3]	54.90%	[3]
Spreads (bps)	4.072%	[3]	4.29%	[3]
Recurring Fair Value Measurements [Member] | Dealer Mark [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	54		144
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			236
Available-for-sale securities	433		1,710
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			14.10%	[3]
Prepayment Speed (%)			3.40%	[3]
Severity (%)			80.00%	[3]
Spreads (bps)			4.22%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			20.40%	[3]
Prepayment Speed (%)			8.30%	[3]
Severity (%)			80.00%	[3]
Spreads (bps)			6.37%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			18.70%	[3]
Prepayment Speed (%)			5.60%	[3]
Severity (%)			80.00%	[3]
Spreads (bps)			5.648%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	0.00%	[3]
Severity (%)	65.00%	[3]	65.00%	[3]
Spreads (bps)	2.25%	[3]	2.99%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	9.10%	[3]	24.30%	[3]
Prepayment Speed (%)	36.20%	[3]	10.90%	[3]
Severity (%)	100.00%	[3]	80.00%	[3]
Spreads (bps)	3.50%	[3]	6.54%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Subprime private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.20%	[3]	15.70%	[3]
Prepayment Speed (%)	6.30%	[3]	2.90%	[3]
Severity (%)	79.80%	[3]	76.70%	[3]
Spreads (bps)	3.164%	[3]	5.27%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	563		636
Available-for-sale securities	2,031		1,911
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	2.90%	[3]	2.60%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	4.05%	[3]	3.75%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	3.459%	[3]	3.204%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	0.963%	[3]	0.77%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	5.45%	[3]	3.75%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	3.30%	[3]	2.977%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities			916
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			4.00%	[3]
Prepayment Speed (%)			0.20%	[3]
Severity (%)			50.00%	[3]
Spreads (bps)			4.31%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			10.00%	[3]
Prepayment Speed (%)			10.00%	[3]
Severity (%)			85.00%	[3]
Spreads (bps)			11.54%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Other [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			5.00%	[3]
Prepayment Speed (%)			3.00%	[3]
Severity (%)			84.80%	[3]
Spreads (bps)			5.886%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	105		87
Available-for-sale securities			3,003
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	10.70%	[3]	5.70%	[3]
Prepayment Speed (%)	4.30%	[3]	0.60%	[3]
Severity (%)	70.30%	[3]	65.00%	[3]
Spreads (bps)			5.26%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	10.80%	[3]	17.60%	[3]
Prepayment Speed (%)	8.40%	[3]	4.00%	[3]
Severity (%)	80.00%	[3]	70.00%	[3]
Spreads (bps)			6.12%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Trading securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	10.80%	[3]	12.50%	[3]
Prepayment Speed (%)	7.20%	[3]	1.70%	[3]
Severity (%)	73.10%	[3]	67.60%	[3]
Spreads (bps)			5.67%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			0.00%	[3]
Prepayment Speed (%)			0.00%	[3]
Severity (%)			50.00%	[3]
Spreads (bps)			2.88%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			23.60%	[3]
Prepayment Speed (%)			20.80%	[3]
Severity (%)			70.00%	[3]
Spreads (bps)			6.43%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow with Inputs [Member] | Alt-A private-label securities [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			6.40%	[3]
Prepayment Speed (%)			7.40%	[3]
Severity (%)			57.20%	[3]
Spreads (bps)			4.428%	[3]
Recurring Fair Value Measurements [Member] | Discounted Cash Flow without Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	146
Recurring Fair Value Measurements [Member] | Internal Model [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	(82)		(130)
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Derivatives	2
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	49	[2]
Available-for-sale securities	18	[2]	39	[2]
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	101		78
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	32
Available-for-sale securities	43		205
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			117
Available-for-sale securities	1,984		688
Recurring Fair Value Measurements [Member] | Other Valuation Technique [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			17
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			44	[2]
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	906		355
Available-for-sale securities	3,882		2,326
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	569		1,009
Recurring Fair Value Measurements [Member] | Consensus without Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	270
Available-for-sale securities	1,117		1,231
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	2,004
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	0.442%	[3]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	5.20%	[3]
Recurring Fair Value Measurements [Member] | Single Vendor With Inputs [Member] | Mortgage revenue bonds [Member] | Available-for-sale securities [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	1.972%	[3]
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Agency [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			27	[2]
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Subprime private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	40		184
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Mortgage revenue bonds [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities			39
Available-for-sale securities	1,721		5,721
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Other [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Trading securities	110
Recurring Fair Value Measurements [Member] | Single Vendor without Inputs [Member] | Alt-A private-label securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Available-for-sale securities	90		45
Recurring Fair Value Measurements [Member] | Fannie Mae [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(324)		(400)
Recurring Fair Value Measurements [Member] | Fannie Mae [Member] | Senior Floating [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(324)		(400)
Recurring Fair Value Measurements [Member] | Fannie Mae [Member] | Discounted Cash Flow without Inputs [Member] | Senior Floating [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(324)		(400)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	2,636		2,634
Long-term debt	(565)		(1,128)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(149)		(271)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Long-term debt [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	2.20%	[3]	1.70%	[3]
Severity (%)	39.30%	[3]	65.00%	[3]
Spreads (bps)	2.25%	[3]	4.68%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Long-term debt [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	21.70%	[3]	9.00%	[3]
Prepayment Speed (%)	31.80%	[3]	14.40%	[3]
Severity (%)	86.50%	[3]	70.00%	[3]
Spreads (bps)	9.75%	[3]	8.51%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus with Inputs [Member] | Long-term debt [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.20%	[3]	6.20%	[3]
Prepayment Speed (%)	12.70%	[3]	10.90%	[3]
Severity (%)	46.00%	[3]	67.50%	[3]
Spreads (bps)	3.963%	[3]	5.843%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt			(330)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Long-term debt [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			0.00%	[3]
Prepayment Speed (%)			0.00%	[3]
Severity (%)			50.00%	[3]
Spreads (bps)			0.98%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Long-term debt [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			10.00%	[3]
Prepayment Speed (%)			100.00%	[3]
Severity (%)			70.00%	[3]
Spreads (bps)			10.30%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Discounted Cash Flow with Inputs [Member] | Long-term debt [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)			5.80%	[3]
Prepayment Speed (%)			36.90%	[3]
Severity (%)			63.40%	[3]
Spreads (bps)			3.314%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Other Valuation Technique [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(73)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Consensus without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(278)		(370)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single Vendor without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Long-term debt	(65)		(157)
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	2,447		2,459
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	1,798		1,698
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.10%	[3]	0.10%	[3]
Prepayment Speed (%)	3.30%	[3]	4.40%	[3]
Severity (%)	3.30%	[3]	5.60%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	93.30%	[3]	99.30%	[3]
Prepayment Speed (%)	33.40%	[3]	92.00%	[3]
Severity (%)	95.40%	[3]	97.30%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Build-Up [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	17.00%	[3]	18.40%	[3]
Prepayment Speed (%)	15.40%	[3]	19.40%	[3]
Severity (%)	27.30%	[3]	33.30%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	142		302
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	0.00%	[3]	0.00%	[3]
Prepayment Speed (%)	2.20%	[3]	1.70%	[3]
Severity (%)	39.30%	[3]	65.00%	[3]
Spreads (bps)	2.25%	[3]	4.68%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	21.70%	[3]	9.00%	[3]
Prepayment Speed (%)	31.80%	[3]	14.40%	[3]
Severity (%)	86.50%	[3]	70.00%	[3]
Spreads (bps)	9.75%	[3]	8.51%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus with Inputs [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	5.20%	[3]	6.40%	[3]
Prepayment Speed (%)	12.80%	[3]	10.40%	[3]
Severity (%)	45.60%	[3]	67.10%	[3]
Spreads (bps)	3.908%	[3]	5.679%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	264		106
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	2.80%	[3]	0.00%	[3]
Prepayment Speed (%)	0.00%	[3]	1.70%	[3]
Severity (%)	39.30%	[3]	65.00%	[3]
Spreads (bps)	2.25%	[3]	5.07%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	20.30%	[3]	8.50%	[3]
Prepayment Speed (%)	12.30%	[3]	14.40%	[3]
Severity (%)	92.20%	[3]	70.00%	[3]
Spreads (bps)	5.13%	[3]	10.30%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Discounted Cash Flow with Inputs [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Default Rate (%)	8.80%	[3]	6.00%	[3]
Prepayment Speed (%)	5.70%	[3]	5.30%	[3]
Severity (%)	67.30%	[3]	65.00%	[3]
Spreads (bps)	3.112%	[3]	7.334%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Consensus without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	243		303
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Single-Family [Member] | Single Vendor without Inputs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value			50
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Mortgage loans held for investment, at fair value	$ 189		$ 175
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Mortgage Loans [Member] | Minimum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	0.79%	[3]	0.77%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Mortgage Loans [Member] | Maximum [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	2.744%	[3]	3.634%	[3]
Recurring Fair Value Measurements [Member] | Consolidated Trusts [Member] | Multifamily [Member] | Build-Up [Member] | Mortgage Loans [Member] | Weighted Average [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Inputs, Quantitative Information [Line Items]
Spreads (bps)	1.293%	[3]	1.545%	[3]

[1] Excludes derivative assets of $1.4 billion and $217 million and derivative liabilities of $1.3 billion and $250 million recognized in our condensed consolidated balance sheets as of September 30, 2013 and December 31, 2012, respectively, that are not subject to an enforceable master netting arrangement or similar agreement.

[2] Includes Fannie Mae, Freddie Mac and Ginnie Mae securities.

[3] Valuation techniques for which no unobservable inputs are disclosed generally reflect the use of third-party pricing services or dealers, and the range of unobservable inputs applied by these sources is not readily available or cannot be reasonably estimated. Where we have disclosed unobservable inputs for consensus and single vendor techniques, those inputs are based on our validations performed at the security level using discounted cash flows.